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Weaverbird nest inspires waste plastic brick

Words:
Stephen Cousins

3D-printed brick mimics lattice nest structure to boost insulation in cavity walls

A thermally efficient brick made of upcycled waste plastic has been developed by researchers at De Montfort University. They claim it could replace the usual foam insulation in cavity wall build-ups.

The brick, which is similar dimensions to a normal clay brick, is 3D printed to form a lattice of plastic strips, inspired by the nest of the Baya weaverbird found on the Indian subcontinent and in Southeast Asia.

The complex structure delivers impressive insulation and structural characteristics. In tests a U-value of 0.25 watts per metre square kelvin (W/m²K) was achieved, roughly 10 times that of a clay brick. Compressive strength can be tuned to between 2 and 50N/mm², where a clay brick measures about 22.5N/mm².

The research team is exploring various construction applications and manufacturing techniques. Current thinking is to create insulation panels of interlocking bricks that would be inserted into cavity walls between the outer wall and concrete blocks.

The nest of the Baya weaverbird inspired the thermally efficient design.
The nest of the Baya weaverbird inspired the thermally efficient design. Credit: De Montfort University Leicester

Project leader Dr Karthikeyan Kandan, senior lecturer in mechanical engineering at De Montfort, says: ‘We are thinking about producing custom made panels for modular homes. An architect would simply give us a dimension and a wall detail etc and we would make large panels of segmented interlocking bricks ready for installation. The challenge of going down the [standalone] brick route is the need to find workers to lay them and the development of glue, which creates issues in terms of bonding and water ingress.’

Kandan says a 3D printed brick costs about £6, but large scale injection moulding or laser cutting could reduce this to less than £1. Different types of plastic waste, from coffee cup lids to plastic bottles, were incorporated into the mix for the bricks. The percentage of each type in the mix resulted in a performance variation of up to 10% in test results. ‘For practical purposes that's nothing and it is faster than having to sort the bottles into different waste stream,’ Kandan says.

Prototype walls were tested in laboratory conditions and real world trials are planned on an full-scale experimental house built by the University in Nigeria, he says. ‘We're going to replace the walls with these plastic brick panels and see if we can build really cheap housing for people living in slums.’

Waste plastic from various sources is used to form the bricks.
Waste plastic from various sources is used to form the bricks. Credit: De Montfort University Leicester

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